1. Field of the Invention
This invention relates to an improvement in the hydroformylation, or oxo, reaction wherein an olefin is reacted with carbon monoxide and hydrogen in the presence of a complex metal catalyst to form aldehydes and/or alcohols.
2. Description of the Prior Art
The hydroformylation, or oxo, reaction is well known in the art and comprises converting an olefin by reaction with carbon monoxide and hydrogen to aldehydes and/or alcohols having one or more carbon atom than the feedstock olefin. The reaction that takes place is an addition at the site of the double bond of the olefin by a hydrogen atom and a formyl group in the presence of a catalyst. Since the formyl group could add to either of the carbon atoms connected by the double bond, isomeric products result from this addition. The hydroformylation conditions of the reactions may be at a temperature of from 75.degree. C. to about 250.degree. C. at a pressure of from about 50 to about 10,000 psig. These hydroformylation conditions are widely used and well known to those in the art.
Many catalysts are known to be useful in the practice of this reaction, most of which comprise a metal from the Group VIII of the Periodic Table of Elements, in complex combination with carbon monoxide and various ligands. The most commonly used metals from this group are cobalt and rhodium. In the past, the most widely used catalyst for the oxo reaction has been dicobaltoctacarbonyl. This catalyst has been prepared from many forms of cobalt by reduction with hydrogen in the presence of carbon monoxide under pressure. However, this catalytic material suffers from several rather serious shortcomings such as its considerable instability during product separation, which precludes simple recovery of the catalyst for use in subsequent reactions. While chemical means exist for the recovery of the cobalt catalyst, they involve additional steps or reactions, increasing the complexity of the overall process and decreasing the commercial profitability of the same. Processes have been developed for the removal of the metal catalyst from the reaction products prior to the separation of the oxo aldehydes and alcohols, but this too is done with considerable difficulty.
In attempts to solve the problems inherent in the use of the metal complex catalyst, various ligands have been added to this complex catalyst mixture in attempts to stabilize the catalyst, both at the hydroformylation reaction conditions and conditions present during product separation. These attempts were made to enable those practicing the hydroformylation or oxo reactions to simply and economically recover the oxo products and recycle the catalyst containing residues for subsequent catalytic activity in the oxo reaction, while not sacrificing the yields of the oxo products by the production of increased reaction residues or production of unwanted by-products, such as paraffin hydrocarbons.
It has been attempted to use various modifiers for the complex catalyst to make it more stable to reaction and product work-up conditions. Various organo compounds of trivalent Group V elements, principally trivalent organo phosphorus or organo arsenic compounds such as organo phosphines, aromatic phosphites and hydrocarbyl arsines, have been complexed with various of the Group VIII metals to form a catalyst for the hydroformylation reaction.
It was previously thought that in order to successfully perform as a ligand in a complex catalyst system for the oxo reaction the compound must have a pair of electrons capable of forming a coordinate bond with the metal atom being complexed and simultaneously having the ability to accept electrons from the metal. The ligands contemplated by the prior art were organo compounds of trivalent phosphorus, arsenic or antimony, containing the trivalent atom having the electronic configuration thought to be necessary for the formation of stable coordinate bonds with the metal. Even when the above requirements for the ligand compound were met, much was left to be desired as far as performance of the complex catalyst was concerned.
However, in spite of the many attempts at improvement, the oxo reaction in the presence of these complex catalyst systems exhibits various problems, such a lack of catalyst stability at reaction and work-up conditions and the inability to recover the catalyst for reuse directly from the reaction products. It is a further disadvantage inherent in the prior art hydroformylation reaction involving mono alpha olefins that there is a relative inability to direct the reactions to the production of a predominantly terminal product when the olefin contains more than two carbon atoms.
While some of the prior art ligands modify the metal catalyst to the point where a predominantly aldehyde product can be produced, their success has been hampered by the inability to achieve high conversion of the olefin to the aldehyde. In addition, it was difficult to recover the aldehyde products from the catalyst-containing residue. Additionally, where emphasis was on high alcohol yields, prior art processes produce an undesirably high amount of paraffin hydrocarbon by-product.
It is therefore an object of the present invention to provide an improved hydroformylation, or oxo process, enabling the more efficient production and recovery of aldehydes and/or alcohols by the catalytic reaction of olefinic compounds with carbon monoxide and hydrogen in the presence of an improved hydroformylation catalyst.
Another object of my invention is the provision of an improved hydroformylation process enabling the efficient recovery by simple distillation of the alcohol and/or aldehyde product from the hydroformylation catalyst which is then recycled for further catalytic reaction in a subsequent hydroformylation reaction.
Still another object of my invention is the provision of an improved hydroformylation process enabling the variance of the relative proportions of the aldehyde and alcohol oxo products while reducing the formation of paraffin by-products.
Still another object of my invention is the provision of an improved hydroformylation catalyst which is stable to hydroformylation reaction conditions and product separation conditions.
Still another object of my invention is the provision of an improved hydroformylation catalyst which, though still mixed with reaction residues, retains its catalytic activity subsequent to the separation of the oxo alcohols and/or aldehydes.
Other objects and advantages of my invention will become apparent to those skilled in the art from the following description thereof.